DNA Barcoding Imagine if every animal came with an easy-to-read barcode, that could identify to which species it belonged! Envision a simple scanner in the future that can get illegal fish or timber out of global markets, ferret out a new pathogen or monitor the environment..costing a couple of dollars and a few hours to get a barcode read.
Traditionally, taxonomy can be tedious, based on careful analysis of the shape of a beak, color of a wing and tiny differences apparent only to an expert eye..which can hit or miss. But in DNA barcoding, scientists simply read out 650 letters of a single gene, called cytochrome c oxidase I (COI), much smaller than the 3 billion letters of the human genome, for example. The COI gene is so variable, that most species have a single, unique code .
There are 160,000 species of butterflies and moths known..about as many more remain to be described. The butterflies in each of the rows below may look the same, but the are easily distinguished by their barcodes.
I find the possibilities for misuse horrifying, to say the least. Imagine if we all came with easily read genetic coding? Those who had a gene that carried a possibility of a child having some genetic abnormality could be forbidden to breed. A government could conceivably use that same code to breed in or out of it’s people those traits they either found desirable or wished to eradicate. Huxley’s “Brave New World” comes to mind. Not a future I care for…
Lee Tucker , no, no..this method can distinguish between different species..not so much individuals among a species (such as you and I, for example). For the latter, genome wide sequencing is already available and is likely to be an important part of individualized medicine in the future..for example, one patient may have a strong reaction to a common drug because of a specific mutation, or different types of breast cancers are known to have unique molecular profiles that have to be treated differently. But you are absolutely right in that the ethics of genomic information are to be debated. Not just governments in a Brave New World, but insurance companies could misuse the information in a much nearer future. New technologies will always be coming, the trick is to use them wisely.
Oh, I see! Thanks for explaining it further for me +Rajini Rao. As to the uses and misuses of genome sequencing and genomic information, there is so much that needs to be established as far as ethics go.
Put this scanner in nanobots and they’ll keep farms safe from pests. This would be an example of a useful use of that barcode
Though I do agree the implications for DNA barcoding are vast, I still think there’s as much to say about it’s incompleteness. Unfortunately COI is only expressed in eukaryotes and bacteria with mitochondria, leaving the other kingdoms* totally out. I think the holy grail of plant genetics and systematics right now is finding the COI of plants (regions like ITS in nDNA or matK or rbcL in ctDNA, all of which are highly conserved but also, as you said, extremely variable). Whereas things are pretty clear in organisms with mitochondrial DNA, they are everything but in those without. Half my research at my home institution as an undergrad dealt with just this, and I’ll spare you the details but suffice it to say that there’s still a lot to be done (when is there not, amiright?). Cool article though!
José P. Llongueras , cytochrome c oxidase not in plant mitochondria, really? It’s the last in the ox phos chain, isn’t it?
I think it is, but apparently not as variable. I couldn’t tell you the exact details, but it doesn’t work to differentiate amongst all the plant species. That’s why they look towards regions like ITS 1 and 2, where your flanked with highly conserved regions but have variable regions in between. And then you get these sequences uploaded from herbarium specimens (where you can have pretty degraded DNA) or other plant samples with internal fungi and the like. There’s no one to regulate what goes up, so you compare your sequence to those on NCBI and you don’t know if yours is right or wrong. It’s actually a pretty big mess. I think for something as complex as plants you’ll eventually have to barcode with something like two regions (COI and matK, for example). I’ve heard scientists talk about how they don’t even believe species exist! haha
“Kress et al. (2005) suggest that the use of the COI sequence “is not appropriate for most species of plants because of a much slower rate of cytochrome c oxidase I gene evolution in higher plants than in animals”.” There it is
Yeah, you’re right in that plant barcode genes are different (apparently, the official barcoding loci are rbcLa and matK from a Nov 11 PlosONE paper)..so there must be a problem using COI. But plant mitos definitely do have cytochrome c oxidase..it’s the terminal acceptor or I’ll eat my bioenergetics hat 🙂
We forget how much more complex and evolved plants really are, with our animal-centric point of view!
Cool..thanks for the clarification!
Haha ya, woops! Maybe a tad overly presumptuous of me 😛
Thanks – checking it out now!
So Beautiful I love it!!!!!!!!!!!!!
Where did you get it?
From the about section of Barcode of Life:
The gene region that is being used as the standard barcode for almost all animal groups is a 648 base-pair region in the mitochondrial cytochrome c oxidase 1 gene (“CO1”). COI is proving highly effective in identifying birds, butterflies, fish, flies and many other animal groups. COI is not an effective barcode region in plants because it evolves too slowly, but two gene regions in the chloroplast, matK and rbcL, have been approved as the barcode regions for plants.
That sums up the discussion I had above with José P. Llongueras , very nicely Kevin.
Your instincts (or more rightly bioenergetics skills) were right!
Sadly, cytochrome c oxidase catches my attention.
Good thing I did not have to eat my hat , even if virtually 😉